Dental retention systems

ABSTRACT

Dental retention systems which facilitate the adjustment or removal of an oral appliance, e.g., a crown or bridge, from a reconfigurable abutment assembly are described. The adjustable abutment assembly may be secured to an anchoring implant bored into the bones within the mouth. The abutment assembly has a projecting abutment portion with one or more shape memory alloy compression plates or elements extending along the projecting abutment portion. Each of the plates has a length with one or more straightened portions and with at least one curved or arcuate portion. Energy may be applied to the elements such that the arcuate portion self-flattens to allow for the oral appliance to be placed thereupon while removal of the energy allows the elements to reconfigure into its curved configuration thereby locking the oral appliance to the abutment. Removal of the oral appliance may be effected by reapplication of energy to the elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/303,764 filed Nov. 23, 2011 which is a divisional of U.S. patentapplication Ser. No. 13/021,579 filed Feb. 4, 2011 which is acontinuation of U.S. patent application Ser. No. 12/504,561 filed Jul.16, 2009, now U.S. Pat. No. 8,047,844; all of which are incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for retaining oneor more dental prostheses in a mouth of a user. More particularly, thepresent invention relates to methods and apparatus for retaining one ormore dental prostheses in a manner which facilitates placement andremoval via an actuation mechanism from an anchoring implant and/orabutment.

BACKGROUND OF THE INVENTION

The use of dental prostheses to replace missing or damaged teeth iscommonplace. Typically, artificial roots, or implants, are implantedinto the bone of the patient's jaw and are used to provide structuralsupport to an intermediate abutment. One or more artificial replacementteeth or crowns are then fastened to the abutment typically by cementsor screws.

FIGS. 1A to 1D illustrate partial cross-sectional side views of oneexample for implanting a typical crown within the mouth of a patient.Depending upon the number of teeth to be replaced, one or more holes maybe bored within the bone of the jaw. As shown in FIG. 1A, a portion ofthe gums or gingiva 14 may be cut open to expose the underlying bone 10,e.g., maxilla or mandible, into which a drill bit 16 may be used to boreopen a hole 12. An anchoring dental implant 18, optionally threaded, maybe implanted within hole 12 and covered by gingival 14 to allow forhealing and for the implant 18 to take hold within bone 10, as shown inFIG. 1B.

Once the implant 18 has been desirably positioned within bone 10, anabutment assembly 20 may be securely attached to implant 18, e.g., by athreaded pin 22 coupling to an implant receiving well 26 defined withinimplant 18 such that abutment 24, which defines a portion projectingthrough gingival 14 from implant 18 once coupled to implant 18, as shownin FIG. 1C. With abutment 24 secured to implant 18, crown 28 whichdefines crown opening 30 may be secured upon abutment 24 by utilizing anumber of securement mechanisms, such as cement or a fastener such as ascrew. Other securement mechanisms have also included interferencefitting such as with a cross-bar or O-ring type attachment, magnets,etc.

Because the implants, abutments, and crowns are subjected to highcompressive and shear forces, initial positioning of the crowns isimportant not only to provide adequate structural support but also toensure patient comfort. However, while utilizing cement to attach thecrown to the abutment initially allows for aligning the crown morenaturally with the dentition of the patient, the tolerance for mistakesis low once the cement has set because of the difficulty and expense inremoving a cemented crown from the abutment. Screw-type retentiondevices may also provide for good securement of the crown to theabutment, but occlusal contact within the patient dentition is oftenmisaligned resulting in a variety of complications. For instance,misaligned crowns result in a compromised occlusal table which in turnmay lead to chipping of the crowns as well as poor aesthetic appearanceof the patient's dentition.

Previous devices have attempted to create removable denture retentiondevices, such as that disclosed in U.S. Pat. No. 5,516,288, which isincorporated herein by reference in its entirety. Such systems aredescribed which implant a screw within the jawbone of the patient whileutilizing an abutment structure coupled to the implant portion via aball joint made of shape memory materials. A restorative crown or dentalreplacement member is then attached to the abutment via conventionalretention methods. However, such a device fails to disclose the use ofshape memory materials utilized in the interaction between the abutmentand the crown or bridge itself, as described in further detail below, assuch an interaction facilitates the retention and retrieval of the crownor bridge from the abutment and/or implant.

Accordingly, there exists a need for methods and devices which areefficacious in facilitating not only the retention of oral appliances orprostheses, such as crowns or bridges, along the dentition of a patientbut also the removal and/or repositioning of the crown or bridge.

SUMMARY OF THE INVENTION

The assemblies described provide for mechanisms and methods tofacilitate the adjustment or removal of an oral appliance or prosthesis,such as a crown or bridge, from a reconfigurable abutment assembly. Inutilizing the abutment assemblies described herein, an anchoring implantmay be bored into the bones within the mouth of the patient to providefor the structural support of the abutment assembly. Moreover, theimplants and abutment assemblies described herein may be utilized in anynumber of locations within the mouth of the patient, for instance, alongthe maxilla or mandible or other locations within the body which maybenefit from an adjustable abutment assembly as described herein.Additionally, although some of the examples illustrate the placementand/or removal of crowns, various other prostheses for placement withinor along the patient dentition may be utilized with the retentiondevices described herein and are not intended to be limited to use withcrowns.

One example of an abutment retaining assembly may have a projectingabutment portion which extends from a first or upper abutment portion toa second or lower abutment portion. A threaded pin may extend from thelower abutment portion for attachment to the implant, which may be boredinto the underlying bone to serve as an anchor. Portions of the abutmentretaining assembly may be fabricated from any number of biocompatiblematerials, e.g., gold alloys, stainless steel, nickel-titanium alloys,etc., and may be sized for positioning along the patient's dentition.

With the projecting abutment portion extending from the upper abutmentportion, an upper retaining plate may be positioned atop the projectingabutment portion to which one or more compression plates or elements areattached. The compression plates or elements may extend along theprojection abutment portion while secured between upper retaining plateand lower retaining portions along the upper abutment portion. The upperretaining plate, as well as the projecting abutment portion, may definean opening for receiving an engagement instrument which may be insertedtemporarily within the opening and used to secure the abutment assemblyto the anchored implant.

The compression plates or elements may be sized to extend longitudinallyalong the projecting abutment portion and may number from one element toas many as practicable depending upon their size, e.g., six elements,which are spaced circumferentially about the portion in a uniformmanner. Each of the plates has a length with one or more straightenedportions with at least one curved or arcuate portion along the length ofthe element which projects radially when each of the one or moreelements are positioned adjacent to one another over portion.

The one or more compression plates or elements may be fabricated fromvarious shape memory alloys, e.g., nickel-titanium alloys such asNitinol, such that the curved or arcuate portion may be preformed alongthe element. A phase change may be initiated in the element upon theapplication of energy, such as heat or electrical energy, to transitionthe element between its martensitic and austenitic phase such that thearcuate portion may self-flatten with respect to the length of theelement. A current or energy, such as an electrical current may beapplied to the one or more elements via an input lead contact and returnlead contact. If more than a single element is utilized, each of theelements may be electrically coupled to one another to allow for each ofthe elements to be energized or heated. As the energy is applied to theone or more elements, the phase change may be initiated such that thearcuate portions of elements reconfigure from their curved shape to astraightened shape.

The crown may define a crown opening which is slightly larger indiameter than the abutment assembly in its straightened configuration sothat as the crown is lowered upon the abutment assembly, the crown maybe tightly fitted thereupon. A portion of the crown opening may furtherdefine a widened diameter formed by, e.g., an undercut, which iscorrespondingly sized to receive the arcuate portions of the elements intheir widened diameter. Moreover, the crown may further definecorresponding input lead contact and corresponding return lead contactwhich are positioned along the crown such that the correspondingcontacts come into electrical communication with their respectivecontacts to allow for the transfer of energy directly through the crownand into the elements when the crown is secured to the abutment.

Once the crown has been desirably positioned upon the abutment assembly,the energy may be removed or ceased such that straightened arcuateportions of the elements reconfigure into their arcuate shape. As thearcuate portions reform, the elements may shorten in length thusretracting the upper retaining plate and radially expanding the arcuateportions into the widened diameter of the crown. The reconfiguredarcuate portions compress the elements against the widened diameterthereby effectively preventing relative movement between the crown andthe elements and locking the crown into position along the abutment.

In the event that the crown requires removal, replacement, orrepositioning upon the abutment, energy may again be applied to theelements positioned within the crown through corresponding contacts. Asthe arcuate portions are reconfigured back into their straightenedlow-profile configurations, the compression against the interior of thewidened diameter may be released and the crown may be adjusted orrepositioned upon the abutment or simply pulled entirely off theabutment assembly. A substitute crown may be replaced upon the abutment,if so desired.

A power source may be electrically coupled to a controller, e.g.,resistance heating controller, to control the current flow to the one ormore elements either directly through the contacts or through thecorresponding contacts. As the controller is utilized to control theamount of current, the one or more elements may rise in temperature dueto resistance heating. The power source may comprise any number of powersupplies, e.g., an AC outlet or batteries, and the power source andcontroller may be configured into various form factors. The powersupplied may range from between, e.g., about 10 to 150 Watts, while theheating time for applying the power may range from, e.g., 0.1 to 2seconds or longer.

Yet another example for a power source for reconfiguring the one or moreelements may utilize inductive heating where the elements may be heatedwithout any direct contact between the power source and the elements. Aninductive heating assembly may be regulated with a controller-likevariable output oscillator circuit which sends an alternating currentthrough a conductor to one or more coils which then generates analternating magnetic field between the coils which may be set apart inapposition and at a distance from one another. The distance between thecoils may define a receiving channel which is sized to be positionedadjacent to or in proximity to the crown and/or one or more elements.

With the abutment assembly and/or crown positioned within the receivingchannel, the alternating magnetic field may be created between the coilsto form eddy currents in the one or more elements which causes thematerial to heat up due to electrical resistance and thus activates theshape memory alloy to initiate their shape change. The frequency of thealternating current and the magnetic field can be set between, e.g., 1kHz and 1 MHz, depending on the size and configuration of the one ormore elements and the targeted activation time. Moreover, the powerconsumption may range between about, e.g., 10 W to 5 kW.

In yet another variation of a dental retaining assembly, a ferromagneticshape memory alloy (FSMA) may be configured to have a taperedcircumferential edge but when exposed to a magnetic field, the plate maybecome reconfigured such that the FSMA plate maintains a straightenedcylindrical shape from its tapered configuration. As the magnetic fieldis maintained, the crown defining a crown opening with a wideneddiameter formed by, e.g., an undercut, may be positioned upon theactuated FSMA plate such that a position of the FSMA plate correspondsto the position of widened diameter. With the crown desirably positionedupon the abutment, the magnetic field may be removed or terminated suchthat the plate reconfigures into its tapered configuration within thewidened diameter and compresses crown into securement upon the abutment.

In yet another alternative, multiple implanted anchoring assemblies maybe secured to the patient to allow for the securement of one or morepartial bridges utilizing the mechanisms and methods described herein.Accordingly, one or more anchoring assemblies may be used to secure oneor more partial bridges. In another example, an overdenture may besecured to the patient utilizing an implanted cross-bar configurationwhich incorporates one or more anchoring assemblies. The anchoringassemblies may similarly utilize the one or more elements to secure theoverdenture within the patient mouth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D illustrate partial cross-sectional profiles of an exampleof placing an implant within a jawbone of a patient and attaching acrown thereto.

FIG. 2A illustrates a perspective view of attaching one variation of anabutment retaining assembly to a conventional implant.

FIG. 2B illustrates a perspective view where energy may be applied toone or more shape memory compression plates or elements positioned alongthe abutment retaining assembly to configure the elements into alow-profile shape such that a crown may be received upon the abutment.

FIG. 2C illustrates a perspective view where the shape memory elementsmay be reconfigured into their expanded configuration to secure thecrown upon the abutment.

FIG. 2D illustrates a perspective view showing how energy may bereapplied to the elements through the crown to yet again configure theelements into a low-profile shape to allow for the repositioning orremoval of the crown from the abutment.

FIG. 3 illustrates an example of how energy may be applied via a powersource and controller to the one or more elements.

FIG. 4 illustrates schematically another example of how an alternatingmagnetic field may be applied to the one or more elements by inductivelytransferring energy to reconfigure the shape of the elements.

FIG. 5 illustrates a housing configured into a mouthpiece for applyingenergy to the compression elements.

FIG. 6A illustrates an example of another variation for securing a crownwhere an abutment retaining assembly is secured to an implant.

FIG. 6B illustrates a reconfigurable ferromagnetic shape memory alloy(FSMA) plate which may be secured to the abutment.

FIG. 6C illustrates a magnetic field applied to the FSMA plate toconfigure its shape into a low-profile to receive a crown.

FIG. 6D illustrates the positioning of the crown upon the FSMA plate andthe reconfiguration of the FSMA plate into its expanded profile tosecure the crown thereto.

FIG. 7A illustrates the removal of the crown from the FSMA plate byapplication of a magnetic field to reconfigure the shape of the plateand allowing for the release of the crown.

FIG. 7B illustrates a partial cross-sectional side view showing thereconfiguration of the FSMA plate and the release of the crown.

FIG. 8 illustrates a representative partial side view of an FSMA plateengaged against a widened diameter of the crown for securing the crownin position.

FIG. 9 shows a perspective view of one or more crowns or bridges whichhave been coupled to implants by utilizing the one or more elements toshow how the crowns or bridges may be positioned along a patient'sdentition to align the occlusal contact points for patient comfort andsafety.

FIG. 10 shows a perspective view of multiple implants and abutmentassemblies utilizing the reconfigurable plates or elements herein tosecure individual crowns or bridges to a patient's bone.

FIG. 11 shows a perspective view of another example where an implantedcross-bar may be utilized to secure an overdenture to the patient's bonevia the reconfigurable plates or elements.

FIG. 12 shows a perspective view of yet another example where one ormore anchoring assemblies may be used to secure a dental prosthesis,such as an overdenture, to the patient's mouth.

FIG. 13 shows yet another example of an anchoring assembly utilizingcompression plates comprised of biased spring elements which arereconfigured by a shape memory wire.

DETAILED DESCRIPTION OF THE INVENTION

In positioning and securing an oral appliance, such as a crown orbridge, within the mouth of a patient, the retaining assembliesdescribed herein allow not only for secure attachment but also foradjustment of the crown or bridge along the patient's dentition. Theassemblies described also provide for mechanisms and methods tofacilitate the entire removal of the crown or bridge from the abutment.In utilizing the abutment assemblies described herein, any number oftypical anchoring implants may be bored into the bones within the mouthof the patient to provide for the structural support of the abutmentassembly. Moreover, the implants and abutment assemblies describedherein may be utilized in any number of locations within the mouth ofthe patient, for instance, along the maxilla or mandible or otherlocations within the body which may benefit from an adjustable abutmentassembly as described herein.

Turning now to FIG. 2A, one example of an abutment retaining assembly 40is illustrated as having a projecting abutment portion 42 which extendsfrom a first or upper abutment portion 44, which is optionally tapered,to a second or lower abutment portion 46. A threaded pin 48 may extendfrom the lower abutment portion 46 for attachment to implant 18, whichmay be bored into the underlying bone 10 to serve as an anchor, and aspreviously described, which may be adjacent to another crown orpre-existing tooth or teeth 68. Portions of the abutment retainingassembly 40 may be fabricated from any number of biocompatiblematerials, e.g., gold alloys, stainless steel, nickel-titanium alloys,etc., and may be sized for positioning along the patient's dentition.For instance, the assembly 40 may have a diameter ranging from, e.g., 2to 6 mm, with a length ranging from, e.g., 5 to 15 mm. These dimensionsare exemplary and are not intended to be limiting.

With the projecting abutment portion 42 extending from the upperabutment portion 44, an upper retaining plate 50 may be positioned atopthe projecting abutment portion 42 to which one or more compressionplates or elements 54 are attached. The compression plates or elements54 may extend along the projection abutment portion 42 while securedbetween upper retaining plate 50 and lower retaining portions 52 alongthe upper abutment portion 44. The upper retaining plate 50, as well asprojecting abutment portion 42, may define an opening 64, which may beoptionally keyed, for receiving an engagement instrument 66 which may beinserted temporarily within opening 64 and used to secure abutmentassembly 40 to the anchored implant 18, e.g., by rotating abutmentassembly 40 so as to screw threaded pin 48 into implant 18.

The compression plates or elements 54 may be sized to extendlongitudinally along projecting abutment portion 42 and may number fromone element to as many as practicable depending upon their size, e.g.,six elements, which are spaced circumferentially about portion 42 in auniform manner. Each of the plates are illustrated as having a lengthwith one or more straightened portions 56 with at least one curved orarcuate portion 58 along the length of the element 54 which projectsradially when each of the one or more elements 54 are positionedadjacent to one another over portion 42, as illustrated.

In one example, each of the elements 54 may range in length from, e.g.,about 5 to 10 mm, with a thickness of e.g., about 0.5 to 1.5 mm.Moreover, the curved or arcuate portion 58 may have a radius whichdefines a height of, e.g., about 1 to 2 mm, relative to the thickness ofthe element 54 such that when element 54 is reconfigured into astraightened configuration, element 54 may extend an additional, e.g.,1.5 to 3 mm in length. These dimensions are provided as exemplary valuesand are not intended to be limiting. Variations in dimensions may beutilized as practicable.

The one or more compression plates or elements 54 may be fabricated fromvarious shape memory alloys, e.g., Nitinol, such that the curved orarcuate portion 58 may be preformed along the element 54. A phase changemay be initiated in the element 54 upon the application of energy, suchas heat or electrical energy, to transition the element 54 between itsmartensitic and austenitic phase such that the arcuate portion 58 mayself-flatten with respect to the length of the element 54. Asillustrated in FIG. 2B, current or energy 70, such as an electricalcurrent i, may be applied to the one or more elements 54 via an inputlead contact 60 and return lead contact 62. If more than a singleelement 54 is utilized, each of the elements 54 may be electricallycoupled to one another to allow for each of the elements 54 to beenergized or heated. The lead contacts 60, 62 may be positioned along asingle element or different elements so long the elements are inelectrical communication. As the energy is applied to the one or moreelements 54, the phase change may be initiated such that the arcuateportions 58 of elements 54 reconfigure from their curved shape to astraightened shape, as shown in the figure.

With the arcuate portions 58 reconfigured into straightened portions58′, upper retaining plate 50 may be moved longitudinally with respectto upper abutment portion 44 while the elements 54 remain attached totheir lower retaining portions 52. The resulting outer diameter of theelements 54 upon the abutment may be reduced from, e.g., about 6 mm toabout 4 mm, to thus allow for the placement of a crown 72 upon theabutment assembly. Crown 72 may define a crown opening 74 which isslightly larger in diameter than the abutment assembly in itsstraightened configuration so that as crown 72 is lowered upon theabutment assembly, crown 72 may be tightly fitted thereupon. A portionof crown opening 74 may further define a widened diameter 76 formed by,e.g., an undercut, which is correspondingly sized to receive the arcuateportions 58 of elements 54 in their widened diameter, as describedbelow. Moreover, crown 72 may further define corresponding input leadcontact 60′ and corresponding return lead contact 62′ which arepositioned along crown 72 such that the corresponding contacts 60′, 62′come into electrical communication with their respective contacts 60, 62to allow for the transfer of energy directly through the crown and intothe elements 54 when the crown is secured to the abutment. To guide thecrown 72 upon the abutment assembly, the opening 74 of crown 72 may beoptionally keyed or shaped in a predetermined manner which correspondswith a configuration of the abutment such that advancement of the crown72 upon the abutment may be achieved in a specified orientation, if sodesired.

Once crown 72 has been desirably positioned upon the abutment assembly,the energy may be removed or ceased such that straightened arcuateportions 58′ of elements 54 reconfigure into their arcuate shape. As thearcuate portions 58 reform, the elements 54 may shorten in length thusretracting upper retaining plate 50 and radially expanding the arcuateportions 58 into the widened diameter 76 of crown 72, as shown in FIG.2C. The reconfigured arcuate portions 58 compress the elements 54against the widened diameter 76 thereby effectively preventing relativemovement between the crown 72 and the elements 54 and locking the crown72 into position along the abutment. The compressive force which may begenerated between the elements 54 and the crown interior may range,e.g., between 10 N to 10 kN, to effectively lock the crown 72 intoposition.

In the event that crown 72 requires removal, replacement, orrepositioning upon the abutment, energy may again be applied to theelements 54 positioned within the crown 72 through correspondingcontacts 60′, 62′ which are in electrical communication with theirrespective contacts 60, 62, as shown in FIG. 2D. As the arcuate portions58 are reconfigured hack into their straightened low-profileconfigurations 58′, the compression against the interior of wideneddiameter 76 may be released and crown 72 may be adjusted or repositionedupon the abutment or simply pulled entirely off the abutment assembly. Asubstitute crown may be replaced upon the abutment, if so desired.

In delivering the energy to the one or more elements 54 for initiatingthe phase change in the shape memory alloy, FIG. 3 illustrates oneexample which delivers a current to elements 54. A power source 80 maybe electrically coupled to a controller 82, e.g., resistance heatingcontroller, to control the current flow to the one or more elements 54either directly through contacts 60, 62 or through correspondingcontacts 60′, 62′ if delivered through crown 72. In either case, as thecontroller 82 is utilized to control the amount of current, the one ormore elements 54 may rise in temperature due to resistance heating. Thepower source 80 may comprise any number of power supplies, e.g., an ACoutlet or batteries, and the power source 80 and controller 82 may beconfigured into various form factors. For example, the heating assemblymay be configured into a hand-held unit which is portable by the user orit may be configured into a larger non-portable unit. Because the size,configuration, and thermal conductivity of the elements 54 may bevaried, the amount of power applied and the heating time may be variedaccordingly. For instance, the power supplied may range from between,about 10 to 150 Watts, while the heating time for applying the power mayrange from, 0.1 to 2 seconds or longer.

Yet another example for a power source for reconfiguring the one or moreelements 54 is illustrated schematically in FIG. 4. Because thisparticular variation may utilize inductive heating, the elements 54 maybe heated without any direct contact between the power source and theelements 54. As shown, an inductive heating assembly 90 may be regulatedwith a controller-like variable output oscillator circuit 92 which sendsan alternating current i through conductor 94 to one or more coils 96,98 which then generates an alternating magnetic field 100 between thecoils 96, 98, which may be set apart in apposition and at a distancefrom one another. The distance between the coils 96, 98 may define areceiving channel 104 which is sized to be positioned adjacent to or inproximity to the crown 72 and/or one or more elements 54 such that whenthe elements 54 are to be reconfigured, the heating assembly 90 may bepositioned upon the abutment assembly and/or crown 72 within the user'smouth.

With the abutment assembly and/or crown 72 positioned within receivingchannel 104, the alternating magnetic field 100 may be created betweencoils 96, 98 to form eddy currents 102 in the one or more elements 54.These eddy currents 102, which may also be described as the movement ofelectrons in the material, causes the material to heat up due toelectrical resistance and thus activates the shape memory alloy toinitiate their shape change. The frequency of the alternating current iand the magnetic field can be set between, e.g., 1 kHz and 1 MHz,depending on the size and configuration of the one or more elements 54and the targeted activation time. Moreover, the power consumption mayrange between about, e.g., 10 W to 5 kW. As described above, the heatingassembly 90 may be configured, e.g., as a portable hand-held unit or asa larger non-portable unit. Additional details and examples of aninductive heating assembly are further shown in U.S. Pat. No. 6,710,314,which is incorporated herein by reference in its entirety.

Additionally in this and other examples, a sealant 106, such as abiodegradable silicone material, may be placed within the crown cavityto at least partially encompass or encase the abutment assembly tocreate a water-tight seal. This sealant 106 may completely encase theabutment assembly or it may seal just around a portion of the assembly,such as upper abutment portion 44.

In applying the energy (either resistive or inductive heating) to theone or more compression elements, one variation of a housing 101configured into the form of a mouthpiece which may be insertedtemporarily into the mouth of a patient is shown in the perspectiveassembly view of FIG. 5. Housing 101 may generally comprise twobiteplates 103 which extend from a handle 111 and which define areceiving cavity 105 for receiving within or placement against a dentalprosthesis such as an overdenture, crown, etc. Other variations maycomprise a single biteplate or a partial biteplate depending upon thedental prosthesis to be secured. Moreover, handle 111, which generallyextends from the mouth of the patient, may be removed or omittedentirely.

In either variation, one or more contacts 109 may be defined along thereceiving cavity 105 and are in electrical communication with a powersupply 107 through electrical conductor 113, which may be routed throughthe housing 101 to each of the respective contacts 109. In use, with oneor more anchoring assemblies 119 secured within the patient's mouth, thedental prosthesis 115 (or prostheses) may either be positioned directlyupon the respective anchoring assembly 119 or the dental prosthesis 115may be positioned within receiving cavity 105 of housing 101. Thehousing 101 may then be positioned within the patient's mouth such thatthe respective dental prosthesis 115 is either placed upon acorresponding anchoring assembly 119 and/or such that the one or morecontacts 109 positioned within housing 101 is aligned with acorresponding contact 117 positioned along the dental prosthesis. Ineither case, once the respective contacts 109, 117 are aligned, powersupply 107 may be activated to actuate the compression plates toreconfigure and secure the dental prosthesis 115 to the one or moreanchoring assemblies 119. Once the dental prosthesis 115 is fullysecured, housing 101 may be removed from the patient's mouth. Housing101 may be reinserted into the patient's mouth to reverse the securementprocess for readjusting or entirely removing the prostheses from theanchoring assemblies 119, if so desired. Moreover, housing 101 may beoptionally used by the patient for inserting and/or removing prosthesessuch as overdentures on a daily basis or it may also be used by apractitioner for securing and/or removing any number of dentalprostheses.

In yet another variation of a dental retaining assembly, FIG. 6Aillustrates an example of an assembly which may utilize a ferromagneticshape memory alloy (FSMA), which are ferromagnetic materials whichgenerally exhibit relatively large changes in shape and size whenexposed to a magnetic field. In this variation, an abutment assemblyhaving a projecting abutment portion 110 extending from an upperabutment portion 44 may be connected to an implant 18 via a threaded pin26, as previously described. With the abutment secured to implant 18, acircular FSMA plate 114 having a tapered circumferential edge may beattached to the abutment opening 112 via a threaded retaining pin 116,which may be optionally keyed with respect to opening 112, as shown inFIG. 6B. Although illustrated as a circular element, FSMA plate 114 maybe configured into various shapes or sizes depending upon the couplingmechanism to the crown.

The FSMA plate 114 may be configured to have a tapered circumferentialedge but when exposed to a magnetic field 124, as shown in FIG. 6C, theplate 114 may become reconfigured such that the FSMA plate 114′maintains a straightened cylindrical shape from its taperedconfiguration. As the magnetic field 124 is maintained, crown 118defining a crown opening 120 with a widened diameter 122 formed by,e.g., an undercut, may be positioned upon the actuated FSMA plate 114′such that a position of FSMA plate 114′ corresponds to the position ofwidened diameter 122. With the crown 118 desirably positioned upon theabutment, the magnetic field 124 may be removed or terminated such thatthe plate 114 reconfigures into its tapered configuration within thewidened diameter 122 and compresses crown 118 into securement upon theabutment, as shown in FIG. 6D. Also as described above, crown 118 may beconfigured to keyed to be positioned upon the abutment in apredetermined orientation, if so desired.

As shown in FIG. 7A, in the event that the crown 118 needs to berepositioned upon the abutment, readjusted, or removed entirely, themagnetic field 124 may be reapplied upon the crown 118 such that FSMAplate 114 reconfigures again from its tapered configuration to itsstraightened cylindrical configuration. FIG. 7B illustrates a partialcross-sectional side view of the FSMA plate 114 reconfigurable betweenits tapered configuration and its straightened configuration 114′. Alsoshown is another variation of the widened diameter utilizing a lockingring 126, which may be alternatively configured to define an undercutthrough which FSMA plate 114 may freely slide when straightened yetwhich interlocks against when the FSMA plate 114 is in its taperedconfiguration.

FIG. 8 illustrates a detail view of the locking interaction between theFSMA plate and the ring 126. With the FSMA plate 114′ in itsstraightened configuration while under the magnetic field 124, plate114′ may freely slide into position through the ring 126. However, uponremoval of the magnetic field 124, the FSMA plate 114′ may reconfigureinto its tapered configuration 114 such that the FSMA plate 114 issecured against the ring 126 to prevent movement of the crown relativeto the plate 114. The plate 114 may be keyed relative to the ring 126such that the crown is fitted upon the abutment in a predeterminedorientation, if so desired.

In determining the amount of retention force retention force beforeyield F_(r) between the plate 114 and the ring 126, the effective stressσ₀ may be initially calculated utilizing the following equation (1)while assuming that the FSMA is isotopic in nature.

$\begin{matrix}{\sigma_{0} = {\frac{1}{\sqrt{2}}\sqrt{\sigma_{n}^{2} + {6\sigma_{t}^{2}}}}} & (1)\end{matrix}$

where σ_(n) represents the normal stress and σ_(t) represents thetangential stress values. Expanding the formula (1) in terms of σ_(u)and Θ which represents the undercut angle, the force may be calculatedutilizing the following equation (2).

$\begin{matrix}{F_{R} = {\frac{2\sqrt{2}A}{\sqrt{\left( {{5\; \cos^{2}2\theta} + {12\; \cos \; 2\; \theta} + 7} \right)}}\sigma_{0}}} & (2)\end{matrix}$

where A represents the nominal cross-sectional area of the plate 114against the ring 126, Θ represents the undercut angle, and σ₀ representsthe effective stress. Thus assuming cos 2θ≈1, the equation (2) forcalculating the retention force may be simply reduced to the followingequation (3).

F _(R)=0.577Aσ ₀  (3)

Because of the adjustable nature of the retention assemblies describedherein, the crowns or bridges secured to the abutment assemblies may beadjusted in vivo to ensure that the dentition, once secured, alignsproperly. As indicated in the perspective view of FIG. 9, multipleanchored crowns 130 as shown which have been secured to the patient. Theresulting occlusal contact points 132, which are those areas along theocclusal surface which contact the opposed tooth or teeth as the jaw isarticulated, may thus be adjusted utilizing the mechanisms and methodsdescribed to ensure proper alignment for patient comfort, safety, andreliability of the crowns.

Although the previous examples have illustrated a single crown placedupon a single corresponding abutment assembly, alternative variationsmay be utilized. For instance, FIG. 10 illustrates an example wheremultiple implanted anchoring assemblies 144 may be secured to thepatient to allow for the securement of one or more partial bridges 140,142 utilizing the mechanisms and methods described herein. Accordingly,one or more anchoring assemblies 144 may be used to secure one or morepartial bridges. In another example, FIG. 11 shows another variationwhere an overdenture 150 may be secured to the patient utilizing across-bar 152 configuration implanted into the patient's bone. Theoverdenture 150 itself may incorporate one or more anchoring assemblies154 which extend away from the overdenture 150 for coupling to thecross-bar 152. The anchoring assemblies 154 may similarly utilize theone or more elements for securing the overdenture 150 within the patientmouth as they may be configured to operate in a similar manner as thosepreviously described. For instance, rather than transitioning from anextended to a compressed configuration for compression against theinterior of the dental prosthesis, anchoring assemblies 154 maytransition from to an extended configuration to a compressedconfiguration which compresses over and/or upon the cross-bar 152 tosecure the overdenture 150 thereto.

In yet another example, as shown in the perspective view of FIG. 12, oneor more anchoring assemblies 144 may be secured to the patient's mouthfor coupling to a dental prosthesis such as an overdenture 150. In thisexample, the overdenture 150 may define one or more receiving channelscorresponding to the one or more anchoring assemblies 144 such thatreconfiguration of the compression plates along anchoring assemblies 144may compress and secure against an interior surface of each respectivereceiving channel in a manner as described above to secure theoverdenture 150 within the patient's mouth. Removal of overdenture 150may be effected utilizing any of the variations described herein toallow for daily removal of overdenture 150, if so desired.

Another variation of the anchoring assembly is illustrated in the sideview of FIG. 13, which shows an anchoring assembly 160 utilizingcompression plates which are comprised of biased elements 162, e.g.,leaf springs, which are prefabricated to be biased in an outwardlyradial direction relative to the abutment assembly 164 to which they aremounted. The biased elements 162 may be fabricated into individualplates from a material such as spring stainless steel which are formedto have a curved or arcuate portion rather than from a shape memoryalloy, as previously described. Thus, when the elements 162 arepositioned within or alone the abutment assembly 164, the curved orarcuate portions may extend radially and function as a biased springelement.

Each of the elements 162 may define a channel or opening through which aseparate shape memory wire 166, such as a wire made from anickel-titanium alloy, may pass through. Shape memory wire 166 may bestretched relatively taut through elements 162 such that when wire 166is energized, as previously described, the wire 166 may shorten inlength to compress the curved or arcuate portions of elements 162 into aflattened configuration against abutment assembly 164 to allow for theplacement or positioning of a dental prosthesis, such as a crown 170,over abutment assembly 164. Once crown 170 has been desirablypositioned, energy may be removed from wire 166 to allow for itsre-lengthening which in turn may allow for elements 162 to relax hackinto its curved or arcuate shape such that elements 162 compress againstthe interior surface of crown 170 thus locking or securing crown 170into position upon the anchoring assembly 160. As previously described,a sealant 168 may also be optionally positioned upon the crown interiorfor forming a water-tight seal against the anchoring assembly 160 toprevent the entry of food and liquids into the crown interior.

The applications of the devices and methods discussed above are notlimited to the securement of crowns or bridges but may include anynumber of further treatment applications where the securement andadjustability of devices within a patient may be utilized. Moreover,such devices and methods may be applied to other treatment sites withinthe body. Modification of the above-described assemblies and methods forcarrying out the invention, combinations between different variations aspracticable, and variations of aspects of the invention that are obviousto those of skill in the art are intended to be within the scope of theclaims.

1. A retention system for retaining a prosthesis onto an implant,comprising: an implant configured to be inserted within a bone in apatient; an abutment securable to the implant; a prosthesis defining areceiving channel for positioning upon the abutment; and, one or moreshape memory elements securable along a portion of the abutment, whereinthe one or more shape memory elements extends radially relative to theabutment when the elements are in a locking configuration such that theone or more shape memory elements are in contact with the prosthesis inthe locking configuration and are secured against the prosthesis;wherein the one or more shape memory elements are actuatable uponapplication of energy to transition between a low-profile configurationwhere the one or more shape memory elements remains retracted and theradially extended locking configuration.